The invention relates to a method for severing slugs from flexible materials, and more particularly to an improved method for forming from a continuous strip of rubber, a plurality of slugs, each being of a precisely determined mass.
As is well understood by those familiar with the fabrication of rubber products, slugs often are produced through the use of a rubber mill which includes a pair of mutually spaced rollers driven at a constant rate for delivering a sheet of rubber of a constant thickness between the bite of the rollers. In practice, rubber heated through internal friction is fed to the bite whereupon a sheet of rubber is caused to adhere to the surface of one of the rollers of the pair to thus form a "band" about the roller with the sheet's thickness being determined by the spacing between the rollers. Frequently, a continuous strip of rubber is severed from the sheet through the use of a pair of coaxially related, mutually spaced rotary knives, or disk cutters, pressed against the roller about which the sheet is banded for thereby severing a continuous strip of rubber from the sheet. As the strip is removed from the sheet a void is caused to appear therein. However, additional rubber fed between the bite serves to fill the resulting void. Thus, the resulting strip, as a practical matter, can be considered to be a strip of an indeterminate length severed from an endless sheet.
Heretofore, a strip of rubber thus derived from a rubber mill has been conveyed by a suitable conveyor to a rubber extruder or, alternatively, deposited on a table and cut into lengths for loading molds of a myriad of configurations. As is recognized by those familiar with the art of fabricating products from rubber stock material, a strip removed from a mill, in the manner aforedescribed, becomes unstressed or relaxed, once it has been severed, whereupon contraction and attendant deformation occurs. Of course, the amount of heat present in the strip and the memory or nerve of the rubber being processed is not precisely predictable and often is non-uniform in nature. Consequently, the cross-sectional dimensions of a given strip cannot be predicated with absolute certainty. Therefore, slugs of rubber derived by severing strips taken from the surface of a roller within a rubber mill tend to be of an inaccurately established mass.
For reasons which should readily be apparent, an appropriate quantity of rubber must be provided for each mold into which a slug is fed in order to assure an economic production of finished products which meet the standards established for high-quality products. For example, where either insufficient or excessive amounts of rubber are fed to a mold the resulting products do not adequately conform to a preselected norm.
In the past, various attempts have been made to overcome the aforementioned disadvantages by extruding the stock rubber and thereafter severing the extrusions, in their relaxed condition. Flying cutters and the like are used for this purpose. In practice, such techniques often are impractical and simply inadequate.
It should therefore be apparent that there currently exists a need for a practical, economic, and efficient method for forming rubber slugs of precisely determined masses for use in economically fabricating finished products from rubber stock material.